1. Technical Field
Various embodiments generally relate to a smart refresh device, and more particularly, to a technology for detecting a repair address and performing smart refresh, thereby improving a refresh characteristic.
2. Related Art
In general, a semiconductor memory device includes a number of memory cells. As processing technologies have been developed and thus the degree of integration is augmented, the number of memory cells gradually increases. If a fail occurs in even any one among memory cells, a corresponding semiconductor memory device misoperates. Therefore, since the semiconductor memory device including a failed cell cannot perform a desired operation, it should be discarded.
Meanwhile, as the degree of integration of a memory increases, an interval between the plurality of word lines included in the memory is reduced. As the interval between the word lines is reduced, a coupling effect between adjacent word lines increases.
Every time data is inputted and outputted to and from a memory cell, a word line toggles between an activated (active) state and a deactivated (inactive) state. In this regard, as the coupling effect between adjacent word lines increases as described above, a phenomenon occurs, in which the data of a memory cell coupled with a word line adjacent to a frequently activated word line is damaged.
Such a phenomenon is called word line disturbance. Due to the word line disturbance, a phenomenon occurs in which the data of a memory cell is damaged before the memory cell is refreshed.
In order to prevent the degradation of data due to the word line disturbance, a method for detecting a word line of which the number of activation times is large and then preventing the degradation of the data of the pluralities of memory cells electrically coupled to word lines adjacent to the detected word line is needed.